This invention relates to a vehicle occupant restraint system.
A known gas bag of a side impact protection system, which includes several chambers, is filled in that compressed gas discharged by a gas generator flows in parallel into several chambers of the gas bag. In a parallel filling method, one difficulty consists in adjusting the internal pressure of gas bags filled in parallel. For this purpose, various gas supply means with integrated gas generators having gas throughputs at different levels are associated to the individual chambers. Another possibility of supplying compressed gas into the individual chambers of the gas bag consists in providing a gas distribution tube which is introduced into the gas bag and which has an axial end to which the gas generator is connected. In this design, long flow paths are obtained, so that the gas generator must have a sufficient output in order to fill the chambers simultaneously.
It is the object underlying the invention to provide a restraint system with a parallel filling of the inflatable elements, where the inflatable elements can better be adapted to their intended use. This is achieved in a vehicle occupant restraint system which comprises a gas supply means which has an outer housing with at least two outlet openings. The restraint system further comprises at least two inflatable elements to which different outlet openings are associated and which are filled in parallel via the associated outlet openings. The outlet openings are designed such that during inflation of the elements gas flow rates through the individual outlet openings to the inflatable elements are different. Since the gas flow rate from the gas supply means into the inflatable element determines the internal pressure existing in each element after a certain period, the internal pressure of the individual inflatable elements can specifically be adjusted in this way and be adapted to the respective application. There are not required any complicated components such as valves, and the size of the restraint system is not increased. In this way, inflatable elements of different sizes can be realized, which have the same internal pressure, although they are filled by the same gas generator.
Advantageously, the outlet openings and the filling volumes of the elements are adjusted to each other such that the gas supply means can generate different internal pressures in the individual inflatable elements. By specifically controlling the internal pressure in the individual inflatable elements it is possible to simultaneously fill several gas bags formed of inflatable elements, which perform different functions, by a single gas generator. Different chambers of a side gas bag can for instance be provided with a different pressure, in order to cushion the vehicle occupant on the one hand, and on the other hand to stabilize the gas bag. At the same time, other gas bags, such as an A-pillar gas bag, a sunroof gas bag or a grab handle gas bag, which should have either a higher or a lower internal pressure than the side gas bag, can be filled in parallel to a side gas bag by a common gas generator.
The control of the gas flow rates is preferably effected in that the outlet openings have different cross-sections. Since the cross-section of an opening determines the amount of gas flowing through it per time unit, i.e. the gas flow rate and thus the pressure achieved after a certain period, the cross-section of the outlet openings provides a simple and inexpensive means for controlling the pressure, which can easily be adapted to the respective application.
Advantageously, the outlet openings are disposed in the outer housing of the gas supply means such that directly upstream of all outlet openings the same pressure exists. In this way, the reproducibility of the gas flow rates through the respective outlet openings is ensured and the safety of the restraint device is increased.
The gas supply means preferably includes a gas generator accommodated in the outer housing, between the gas generator and the outer housing a pressure compensation space being formed. This pressure compensation space ensures that on the upstream side of each outlet opening the same pressure exists.
In a preferred embodiment of the invention, the inflatable elements and the gas supply means form a gas bag module which preferably is a side gas bag module disposed along the roof frame of the vehicle, the side gas bag module comprising at least one inflatable element which at least partly covers at least one side pane of a vehicle. Especially in the case of side gas bags which have large dimensions and are divided into several chambers, it may be desirable that the individual chambers have different internal pressures. A chamber covering a relatively small window in the rear of the vehicle may for instance be designed softer than a chamber which must absorb the impact of the driver or the passenger and at the same time prevent that the same is flung through the opening of a relatively large side window.
In a preferred embodiment of the invention, the gas supply means has two axial ends, the outlet openings being disposed at the axial ends and the gas generator being disposed at the roof frame behind a vehicle front seat and in front of the seat of a rear occupant, and one inflatable element each extending from the axial ends of the gas supply means to the front and to the rear. In this way, the vehicle occupant restraint system can be designed in space-saving way. There may for instance be used a tubular gas generator, so that the gas supply means can adopt a narrow, elongated shape. Due to the fact that the gas supply means is disposed in the roof frame approximately in the vicinity of the B-pillar, the flow paths for the compressed gas are kept short. The connections to the individual inflatable elements can likewise extend along this longitudinal axis, so that no additional space is required.
Advantageously, at least two inflatable elements are coupled with each other via a non-inflatable connecting member. There may, for instance, be used a known gas bag structure, in which two pieces of fabric are sewn, woven or bonded to each other such that the entire gas bag covers the side pane area from the A-pillar to the C-pillar, darts dividing the gas bag into individual chambers which are not connected with each other and are separated from each other by pieces of fabric without flow connection to the gas generator.
In accordance with a further preferred embodiment of the invention at least two separate gas bags are provided, which are formed of inflatable elements. The advantage is that material is saved, as the gas bag can be placed precisely at the respectively required point. In another embodiment it is possible that e.g. two elements are combined to form a side gas bag, whereas a third element forms an independent gas bag separate therefrom.
It is particularly advantageous when such a separate gas bag extends along the front roof frame and covers this part of the roof frame, this gas bag being in flow connection with the gas supply means for the remaining chambers. A gas bag at this place protects the head of a vehicle occupant bent forward in the case of a side impact.
In accordance with a further embodiment of the invention, the gas bag extending along the front roof frame constitutes an elongated tube, below which in the inflated condition a gas bag is disposed, which at least partly covers the front side pane. Such combination of a side gas bag and an A-pillar gas bag, which covers part of the roof frame, provides an optimum protection for a vehicle occupant on one of the front seats.